First of all, abbreviations of the invention are defined as follows:
3GPP: 3rd generation partnership project, which is a leading group for constituting 3G technical specification.
LTE: long term evolution, which is a long term evolution project for a radio access network, started by 3GPP in December, 2004.
UTRA: Universal Terrestrial Radio Access.
E-UTRA: Evolved-UTRA.
UTRAN: Universal Terrestrial Radio Access Network.
E-UTRAN: Evolved-UTRAN.
eNB: Evolved-NodeB.
IP: Internet Protocol.
SAE: System Architecture Evolution.
OFDM: Orthogonal Frequency Division Multiplexing.
SC-FDMA: Single Carrier-Frequency Division Multiple Access.
RRC: Radio Resource Control.
RLC: Radio Link Control.
SRB1: Signalling Radio Bearer 1.
UE: User Equipment.
A robust mobile communication system can be continuously enhanced as requirements increase, and can provide higher data rate for users and better coverage as well as bigger capacity for networks. For these considerations, and driven by the technology, 3GPP started up a long term evolution (LTE) project for a radio access network, an evolved access technology E-UTRA and an evolved access network E-UTRAN, and a packet-domain core network evolution project SAE facing all-IP, in December, 2004. They expected to provide a better support for the increasing requirements of operators and users by continuing evolution and enhancement from radio interfaces to a core network, to keep the first-mover advantage of technology in the field of mobile communications.
The LTE is a technology based on an OFDM/SC-FDMA, and main performance objectives of the 3GPP LTE project include:
providing a peak rate of 100 Mbps for the downlink and 50 Mbps for the uplink within a spectral bandwidth of 20 MHz;
is improving users' performance at the edge of cells;
increasing the capacity of cells;
reducing the delay of the system, making the time delay of unidirectional transmission of a user plane lower than 5 ms, making the migration time from a sleeping state to an activated state less than 50 ms, and making the migration time from a resident state to an activated state less than 100 ms;
supporting the cell coverage with a 100 Km radius;
being capable of providing an access service with the rate more than 100 kbps for mobile subscriber with a high speed of 350 Km/h; and
supporting paired or unpaired spectrum, and being capable of flexibly allocating multiple bandwidths from 1.25 MHz to 20 MHz.
A procedure of RRC connection re-establishment is described in 3GPP RRC protocol. The object of the procedure is to re-establish the RRC connection, which includes restoring SRB1 and reactivating the security. FIG. 1 is a procedure of RRC connection re-establishment (successfully), which includes the following steps from step S01 to step S03 as shown in FIG. 1.
Step S01, in the case that the security has been activated, in order to keep the RRC connection, the UE at the state of connection (RRC_CONNECTED) sends an RRC connection re-establishment request message (RRCConnectionReestablishmentRequest) to the network side.
Step S02, the network side receives the re-establishment request sent from the UE and delivers an RRC connection re-establishment message (RRCConnectionReestablishment). After the UE receives the message, related procedures are as follows:
1. stopping related timers;
2. restoring SRB1 according to the configuration of radio resource;
3. configuring integrality protection used previously for the bottom layer reactivation; and
4. configuring a encryption algorithm used previously for the bottom layer reactivation.
Step S03, The UE sends an RRC connection re-establishment complete message is (RRCConnectionReestablishmentComplete) to the network side, then the procedure of RRC connection re-establishment ends.
There are many scenarios for initiating an RRC connection re-establishment. Four types of occasions defined in 3GPP RRC protocol, on which a UE needs initiating an RRC connection re-establishment request, include:
1. the UE detects that radio links fail;
2. the cell handoff fails in an E-UTRAN;
3. the RLC identification reaches the maximum retransmission time, and needs to be reset; and
4. an RRC connection reconfiguration fails, including:
A. measurement configuration fails;
B. mobility control (including security configuration), i.e. handoff, fails;
C. the configuration of non-access stratum dedicated information fails;
D. the configuration of dedicated radio resource fails; and
E. the configuration of the information related to the UE fails.
In related techniques, when each scenario happens, the network side knows nothing about the particular reason why the UE initiates a connection re-establishment request, so it cannot make different processes with respect to the different re-establishment requests.